**Core Concept**
The patient's presentation is suggestive of a granulomatous disease, likely tuberculosis (TB), given the presence of bilateral nodular lesions on shins (tuberculids) and bilateral hilar lymphadenopathy on chest X-ray. The Mantoux test, also known as the tuberculin skin test (TST), is used to assess the immune response to Mycobacterium tuberculosis. A positive result, indicated by an induration of ≥ 10 mm in a healthy individual, suggests infection or exposure to TB.

**Why the Correct Answer is Right**
The skin biopsy in this case would likely reveal granulomatous inflammation, characterized by the presence of epithelioid cells, Langhans giant cells, and a mixed inflammatory cell infiltrate. This is a hallmark of TB infection. The lymphocytic response to the Mantoux test, as indicated by the 5 mm induration, suggests a strong immune response to TB antigens, consistent with a diagnosis of TB infection or disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the skin biopsy would not typically reveal a fungal infection such as histoplasmosis, which may present with similar symptoms but would have different histopathological features.
**Option B:** This option is incorrect because the skin biopsy would not reveal a bacterial infection such as staphylococcal scalded skin syndrome, which would have a different clinical presentation and histopathological features.

**Clinical Pearl / High-Yield Fact**
In patients with a positive Mantoux test, it is essential to consider other causes of granulomatous inflammation, such as sarcoidosis or histoplasmosis, especially in regions where these diseases are endemic.

**Correct Answer:** C.